A bone fracture is a traumatic disruption of the continuity of a bone. If there is relative motion of the bone fragments at the fracture site irritation of the surrounding tissues and heavy pain ensue and the time of fracture healing is usually extended. Proper rejoinder of bone fragments is thus dependent upon immobilization of the fracture site. Classically, bone fragment reduction (bone fragments properly aligned and abutted along the fracture line) and immobilization for fractured limb bones has been accomplished by external limb casts. Such casts must be worn for long periods of time, are heavy and unbalancing to the body skeletal structure and muscular system, inhibit bone vascularity (promotes fast and effective bone healing), and may result in bone resorption because of the total absence of tensile and compressive functional loading throughout the fractured bone structure. Fractures in bones other than the arms and legs are more difficult to immobilize and the use of exterior casts may not be possible.
Over the past twenty years the use of compression plate techniques for internal fixation of fractures have been developed and widely applied. With internal fixation, by means of bone screws and compression plates (particularly plates made of biocompatible metals and metal alloys (such as titanium and stainless steel), immediate and absolute immobilization is achieved through interfragmentary compression. Other materials and devices such as wires, intramedullary nails or externally fixed pins are used mainly to reduce bone fracture mobility and improve the position of the fracture segments. The aim of internal bone fracture fixation is to allow early, pain-free movement of the injured limb, mandible, etc., thus avoiding the consequences of long lasting immobilization, i.e., bone fracture disease, bone resorption, etc.
With internal bone fixation it is important that the application of the compression plate or fracture reduction device result in relative immobility of the bone fragments and tight closure of the fracture interface. Without such immobility and tight closure, changing tension and compression loads tend to produce relative motion between the fracture fragments with resultant undesirable fragment shortening due to bone resorption. Through the proper use of a bio-compatible metallic fracture reduction device (a surgically applied implant), static forces applied as interfragmentary compression by the device prevent relative motion between the fracture surfaces. Thus, compressive pre-loading of the bone fragments (through the compression device) prevents relative motion at the fracture site in spite of functional use of the limb, mandible, etc., without external immobilization or splinting. With mechanical stimuli (forces and motion permitted via the internal bone fixation technique, rapid and healthy healing of the fracture is promoted and bone vascularity is maintained and restored. Vascularity of bone is interrupted by the fracture trauma and by surgical intervention (application of the compression device) but revascularization is restored and enhanced by the rigid immobilization of the bone fragment or fracture interfaces through internal fixation techniques.
During the early application of compression device techniques, the devices were meant to be merely fixed to the bone fragments of the fracture for alignment purposes. Later, the value of interfragmentary compression, through devices and plates applied under tension, was recognized. A number of internal fixation devices have been developed with built-in compression devices--devices for tensioning the device or plate to create interfragmentary compression. Some of such systems have required that the plate-tensioning device remain implanted with the plate. Other systems have been designed with removable plate-tensioning apparatus.
Further developments in compression plate designs and attachment screws (also formed of bio-compatible metals and metal alloys) have related to screw head and screw hole geometry, i.e., conical geometry of the screw shoulder and oval screw holes in the compression plate for promoting bone fragment compression during screw application. Attempts to obtain optimal stability of fixation have most recently resulted in the use of congruent fitment between screw and screw hole including both conical counter-sunk screw holes and hemicylindrical screw holes.
Numerous problems remain in the application of the various compression plate systems that are commercially available for internal bone fixation. Some systems require great care in the installation of bone screws so that their orientation is always perpendicular to the plate. When contouring a plate to fit a curved bone surface, circularly fitting screw holes may become distorted and cause high friction against screw rotation or may completely inhibit a screw from entering the screw hole. Built-in tensioning devices associated with some compression plates increase the number of crevices between opposed metal surfaces and promote metal corrosion. Removable plate tensioning devices necessitate generally wider (size) and longer (time) surgical exposure. Buckling or kinking of the bone fragments at the fracture line may occur as a result of improper tensioning at the end of the compression plate during plate application.
In U.S. Pat. No. 4,441,181 granted to H. S. Wevers et al there has been disclosed a bone clip for the surgical repair of bones with the clip having body portions with spaced parallel connecting legs at each side thereof. The clip is designed for use in surgically straightening a bone. A V-notch is cut into the bone and pin holes are drilled into the bone on each side of the notch to receive legs depending from the body portions of the clip at each end thereof. After insertion of the clip legs into the pin holes, the spaced parallel legs are deformed inwardly so as to draw the legs together towards each other to force closure of the V-notch cut into the bone and thereby straighten such bone. The Wevers et al bone clip provides no positive connection of the clip to the bone as by threaded bone screws and there is no elongated support to the bone so as to avoid flexure because there is only one connection point of the clip (depending leg) on each side of the cut V-notch.
Applicant of the present invention, in U.S. patent application Ser. No. 07/069,644 filed July 6, 1987 and entitled "Bone Fracture Reduction Plate and Method of Internal Fixation of Bone Fractures," has disclosed a bone compression plate (formed of bio-compatible metal or metal alloy) provided in its central portion with a compression adjustment aperture of ovate configuration. During application of the compression plate to a bone fracture, the adjustment aperture in the plate is situated over the fracture line and the plate (at each side of the fracture line) is secured to the bone sections on each side of the fracture line by bone screws. The combination of the plate and screws comprises an internal compression fixation system. To tension the plate and thereby apply compression forces or loading to the fracture interface of the bone fragments, transverse spreading forces are applied to the parallel legs of the adjustment aperture of the plate with the result that such legs are permanently deformed (bent) outwardly and the compression plate is reduced in its length thereby forcing the bone fragments into high compression interface relationship along with strong immobilization of the bone fragments. The compression plate design disclosed in U.S. application Ser. No. 07/069,644 offers significant advantages with respect to bone repair and healing, including: full closure of the fracture line and maintenance of interface compression; no requirement of a built-in plate tensioning device or use of removable tensioning apparatus; short term of the surgical intervention for installation of the compression plate with minimal bone exposure and time of bone exposure; no remaining bone gaps; and no buckling or kinking of the bone fragments at the fracture line because of improper tensioning.
It is a principal object of the present invention to provide a unique bone fracture reduction device of relatively small but effective structure for use in internal fixation of fractures.
It is a further object of the invention to provide a bone fracture device for use in the internal reduction and fixation of bone fractures, which may be rapidly and easily installed over a bone fracture or multiplicity of fracture lines and adjusted in place to completely close the one or more fractures and apply appropriate compression loads to the fracture fragments.
It is still a further object of the invention to provide a bone fracture strapping device, for use in the internal fixation of bone fractures and immobilization of the fracture fragments, which may be installed over a bone fracture or interconnected system of bone fractures during short-term surgical intervention and adjusted (after affixation to the bone fracture fragments) to accomplish fracture line closure and apply appropriate compression loads to the fracture fragments to promote rapid bone healing.
It is yet another object of the present invention to provide a unique method for surgical internal fixation of bone fractures and immobilization of the fracture fragments to promote rapid bone healing.
Other objects and advantages of the invention will be apparent from the following summary and detailed description of the bone fracture reduction device of the invention and of the internal bone fixation methodology of the invention taken together with the accompanying drawing figures.